1. Field of the Invention
The present invention relates generally to imaging of three-dimensional (xe2x80x9c3Dxe2x80x9d) volume data sets. More particularly, the present invention relates to improved imaging and analysis of physical attributes representing events within 3D volume data sets.
2. Related Art
Many fields of endeavor require the analysis and imaging of 3D volume data sets. For example, in the medical field, a computerized axial tomography (xe2x80x9cCATxe2x80x9d) scanner or a magnetic resonance imaging (xe2x80x9cMRIxe2x80x9d) device is used to produce a picture or diagnostic image of some part of a patient""s body. The scanner or MRI device generates a 3D volume data set that needs to be imaged or displayed so that medical personnel can analyze the image and form a diagnosis.
Three-dimensional volume data sets are also used in various fields of endeavor relating to the earth sciences. Seismic sounding is one method for exploring the subsurface geology of the earth. An underground explosion or earthquake excites seismic waves, similar to low frequency sound waves, that travel below the surface of earth and are detected by seismographs. The seismographs record the time of arrival of the seismic waves, both direct and reflected waves. Knowing the time and place of the explosion or earthquake, the time of travel of the waves through the interior can be calculated and used to measure the velocity of the waves in the interior. A similar technique can be used for offshore oil and gas exploration. In offshore exploration, a ship tows a sound source and underwater hydrophones. Low frequency (e.g. 50 Hz) sound waves are generated by, for example, a pneumatic device that works like a balloon burst. The sounds bounce off rock layers below the sea floor and are picked up by the hydrophones. In this manner, subsurface sedimentary structures that trap oil, such as faults, folds, and domes, are xe2x80x9cmappedxe2x80x9d by the reflected waves. The data is processed to produce 3D volume data sets that include a reflection or seismic amplitude datavalue at specified (x, y, z) locations within a geographic space.
A 3D volume data set is made up of xe2x80x9cvoxelsxe2x80x9d or volume elements having x, y, z coordinates. Each voxel has a numeric data value for some measured or calculated physical property, at a given location. A data value may, for instance, be an eight bit data word which may include 256 possible values. Examples of geological data values include amplitude, phase, frequency, and semblance. Different data values are stored in different 3D volume data sets, wherein each 3D volume data set represents a different data value. In order to analyze certain geological structures referred to as xe2x80x9ceventsxe2x80x9d, information from different 3D volume data sets must be interpreted and then used to analyze different events.
One conventional method of displaying multiple 3D volume data sets requires that the voxels be resealed in order that the data values from each 3D volume data set fit within the 256 data value range for color display which causes a reduction in accuracy of each 3D volume data set. Another conventional method displays each 3D volume data set, however, controls the visual display of each 3D volume data set by adjusting transparency.
In an article written by Jack Lees, in March 1999, published in The Leading Edge, entitled xe2x80x9cConstructing Faults from Seed Picks by Voxel Tracking,xe2x80x9d two 3D volume data sets, each using only 128 data values of a 256-data value range, are combined in a single display. The display resolution was significantly reduced, thereby limiting the ability to accurately interpret certain events.
Consequently, there is a need in the art for a system and method to visualize one or more 3D volume data sets with improved accuracy and resolution. Those skilled in the art have therefore long sought and will greatly appreciate the present invention which addresses these and other problems. For purposes of describing the present invention, the terms xe2x80x9cimagexe2x80x9d and xe2x80x9cvisualizexe2x80x9d may be interchangeably used.
It is, therefore, an object of the present invention to provide an improved system and method for visualizing and interpreting multiple 3D volume data sets in a single combined 3D volume data set.
It is another object of the present invention to provide an improved system and method for visualizing and interpreting a single 3D volume data set in a single enhanced 3D volume data set.
It is still another object of the present invention to provide an improved system and method for visualizing and interpreting one or more 3D volume data sets using a base 3D volume data set scaled across 256 points, wherein select data values from the one or more 3D volume data sets may be inserted into the base 3D volume data set without changing the scaling of the base 3D volume data set.
An advantage of the present invention is improved resolution of selected events.
Another advantage of the present invention is the ability to accurately and efficiently display selected data values related to an event from more than two 3D volume data sets.
Yet another advantage of the present invention is the ability to display data values from multiple 3D volume data sets at the same time.
Yet another advantage of the present invention is greater accuracy than transparency displays.
Yet another advantage of the present invention is the ability to focus on key events in lower quality data value ranges.
Yet another advantage of the present invention is the reduction in interpretation cycle time.
These and other objects, features, and advantages of the present invention will become apparent from the drawings, the descriptions given herein, and the appended claims.
Therefore, the present invention provides a system and method for imaging one or more 3D volume data sets for purposes of more accurately and efficiently analyzing and interpreting different selected events. Each 3D volume data set comprises a plurality of voxels wherein each voxel comprises a data value positioned at a 3D location in a respective 3D volume data set. One preferred embodiment includes a method of combining multiple 3D volume data sets by selecting a first 3D volume data set representing a first attribute, selecting a second 3D volume data set representing a second attribute, and rendering an output 3D volume data set by comparing each of the data values in at least one of the first 3D volume data set and the second 3D volume data set with a preselected data value range or criteria. For each data value where the criteria are met, the method further comprises inserting a first selected data value at a position corresponding with the respective data value in the output 3D volume data set. For each data value where the criteria are not met, the method further comprises inserting a second selected data value at a position corresponding with the respective data value in the output 3D volume data set. The method may further comprise displaying at least one section of the output 3D volume data set and selecting a data value by inserting a seed pick in the display for visualizing and interpreting an event.
The first selected data value may be related to the first attribute and the second selected data value may be related to the second attribute. The seed pick is visually positioned at a selected data value using the display of the output 3D volume data set. A computer and software program are preferably used for identifying or xe2x80x9cauto-pickingxe2x80x9d all data values connected to the seed pick having the same or similar data value as the respective seed pick. Thus, the present invention may comprise a program storage device readable by a machine, embodying a program of instructions executable by the machine to ultimately image the output 3D volume data set.
In a preferred embodiment, the first 3D volume data set and the second 3D volume data set each comprise seismic data. The method also permits additional 3D volume data sets to be combined and therefore, may include producing a third 3D volume data set representing a third attribute, and comparing each of the data values therein against a second preselected data value range.
In another embodiment of the present invention, an enhanced 3D volume data set related to one of a plurality of attributes may be used to visualize and interpret different selected events. In this embodiment, the method includes identifying each data value from a 3D volume data set which represents a particular attribute. An enhanced 3D volume data set is then created by selecting a data value range or criteria and comparing each data value with the criteria. If the criteria are met, then the method further comprises inserting a first selected data value at a position corresponding with the respective data value in the enhanced 3D volume data set. If the criteria are not met, then the method comprises leaving the data value unchanged in the enhanced 3D volume data set. Additional steps may include displaying at least a section of the enhanced 3D volume data set, selecting a data value by inserting a seed pick in the display, and auto-picking a plurality of data values connected to the seed pick which have a data value identical to that of the seed pick.
In another embodiment of the present invention, a method is provided for creating a combined 3D volume data set derived from multiple 3D volume data sets. The method comprises selecting a base 3D volume data set wherein the base 3D volume data set may comprise data values having a 3D coordinate and a base dataword. The base dataword may preferably be related to a first attribute. Additionally, the method comprises selecting a second three-dimensional volume data set where the second 3D volume data set may comprise data values having a spatially coincident coordinate with respect to the base 3D volume data set and a second dataword related to a second attribute. The method further comprises rendering a combined 3D volume data set by selecting data values in the second 3D volume data set based on a preselected data value range or criteria. If the criteria are met, then the method further comprises replacing the base dataword at a respective coordinate in the base 3D volume data set with a selected data value related to the second attribute. If the criteria are not met, then the method comprises leaving the base dataword related to the first attribute at the respective coordinate in the base 3D volume data set unchanged. After creating the combined 3D volume data set, the method may further comprise displaying at least a portion of the combined 3D volume data set and positioning a seed pick on an event using the display. In one embodiment of the invention, the event is a geological structure.
Continuing in this manner, additional method steps may include selecting a third 3D volume data set where the third 3D volume data set may include data values having a spatially coincident coordinate with respect to the base 3D volume data set and a third dataword related to a third attribute. The method then comprises rendering a revised combined 3D volume data set by selecting data values in the third 3D volume data set based on a second preselected data value range or criteria. If the second criteria are met, then the method further comprises replacing the base dataword at the respective coordinate in the base 3D volume data set with a second selected data value related to the third attribute. If the second criteria are not met, then the method further comprises leaving the base dataword related to the first attribute at the respective coordinate in the base 3D volume data set unchanged. In a preferred embodiment, the first attribute, the second attribute, and the third attribute are each related to seismic data.